Virus capsid expansion driven by the capture of mobile surface loops.
The capsids of tailed-DNA bacteriophages first assemble as procapsids, which mature by converting into a new form that is strong enough to contain a densely packed viral chromosome. We demonstrate that the intersubunit crosslinking that occurs during maturation of HK97 capsids actually promotes the structural transformation. Small-angle X-ray scattering and crosslinking assays reveal that a shift in the crosslink pattern accompanies conversion of a semimature particle, Expansion Intermediate-I/II, to a more mature state, Balloon. This transition occurs in a switch-like fashion. We find that crosslink formation shifts the global conformational balance to favor the balloon state. A pseudoatomic model of EI-I/II derived from cryo-EM provides insight into the relationship between crosslink formation and conformational switching.
Lee
Kelly K
KK
Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Gan
Lu
L
Tsuruta
Hiro
H
Moyer
Crystal
C
Conway
James F
JF
Duda
Robert L
RL
Hendrix
Roger W
RW
Steven
Alasdair C
AC
Johnson
John E
JE
D036022:Capsid Proteins / Q000737:chemistry* / Q000378:metabolism*; D008954:Models, Biological; D008958:Models, Molecular; D009068:Movement; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D014771:Virion / Q000737:chemistry / Q000378:metabolism; D019065:Virus Assembly / Q000502:physiology*
D036022:Capsid Proteins; D046912:Multiprotein Complexes